Olefin resins such as polypropylene and olefin rubbers such as an ethylene-propylene copolymer rubber have excellent physical properties and are relatively inexpensive, and therefore, are widely used. However, olefin resins and rubbers do not have a polar group in the molecule, and a coating film and an adhered layer, formed thereon, have a poor adhesive force to the resins and rubbers, and thus a practically acceptable bond strength is difficult to obtain.
To solve the above-mentioned problems of olefin resins, proposals have been made of incorporating in the olefin resins modifiers such as a polycarbonate diol (Japanese Publication of Unexamined Patent Application [abbreviated to "JP-A"] No. H6-172596) and a diol-terminated polyether-ester prepared by a ring-opening polymerization of a lactone such as .sup.a -caprolactone, with ethylene glycol (JP-A H6-116472) whereby the surfaces of olefin resin articles are modified. The modifiers used have a problem such that they do not have a sufficient compatibility with the olefin resins and the coating properties are not improved to a satisfying extent.
To solve the problems of olefin rubbers, proposals have been made of incorporating in the olefin rubbers modifiers such as a polyhydroxypolybutadiene such that at least 98% of the double bonds have been hydrogenated (Japanese Publication of Examined Patent Application [abbreviated to "JP-B"] No. S57-6462), a hydroxyl-terminated hydrocarbon polymer such as a polyhydroxypolyolefin (JP-A H1-197534), and a low-molecular-weight polyisoprene such that at least 50% of the double bonds have been hydrogenated (JP-A H2-69545). However, the modifier-incorporated olefin rubbers still exhibit a poor adhesive force to a coating.
Recently the present inventors have found that a polyester with a hydroxyl value of at least 30 mgKOH/g, prepared by a polycondensation of a polycarboxylic acid predominantly comprised of a dimer acid of polymerized fatty acid with a polyhydric alcohol, exhibits an excellent compatibility with resinous polymers such as an olefin resin, and a greatly enhanced coatability, and filed a patent application (Japanese Patent Application No. H7-51955). However, the polyester derived from a polycarboxylic acid predominantly comprised of a dimer acid of polymerized fatty acid is generally liquid and has a poor handling property. It is thus desired to provide a modifier for modifying resinous or rubbery polymers, which has a high softening point and is capable of being handled in a solid form, and has excellent compatibility with the resinous or rubbery polymers and coatability.